international Journal of Systematic Bacteriology (1 998), 48, 103 1-1 035 Printed in Great Britain Bacillus pseudomycoides sp. nov. L. K. Nakamura Tel: + 1 309 681 6395. Fax: + 1 309 681 6672. e-mail:
[email protected] Microbial Properties Previous DNA relatedness studies showed that strains identified as Bacillus Research, National Center mycoides segregated into two genetically distinct yet phenotypically similar for Agricultural Utilization Research, Agricu Itura I groups, one being B. mycoides sensu stricto and the other, an unclassified Research Service, US taxon. In the present study, the taxonomic position of this second group was Department of assessed by measuring DNA relatedness and determining phenotypic Agricu Iture, Peoria, IL 61604, USA characteristics of an increased number of B. mycoides strains. Also determined was the second group's 165 RNA gene sequence. The 36 B. mycoides strains studied segregated into two genetically distinct groups showing DNA relatedness of about 30%; 18 strains represented the species proper and 18 the second group with intragroup DNA relatedness for both groups ranging from 70 to 100%. DNA relatedness to the type strains of presently recognized species with G+C contents of approximately 35 molO/i (Bacillus alcalophilus, Bacillus cereus, Bacillus circulans, Bacillus lentus, Bacillus megaterium and Bacillus sphaericus) ranged from 22 to 37%. Although shown to be genetically distinct taxa, the two B. mycoides groups exhibited highly similar (98%) 165 RNA sequences. Phylogenetic analyses showed that both B. mycoides and the second group clustered closely with B. cereus. Although not distinguishable by physiological and morphological characteristics, the two B. mycoides groups and B.